Process for converting cobalt compounds to cobalt acetate and/or cobalt propionate



April 12, 1966 ACETATE AND/OR COBALT PROPIONATE B. H. GWYNN ETAL 3,246,024 PROCESS FOR CONVERTING COBALT COMPOUNDS TO COB ALT Filed Oct. 16, 1962 BERNAQFYW$NN mum/14 .4. pmass JO/l/V V. MR0

ATTORNEY.

United States Patent @fitice 3 24-5 024 rnocuss non conyrzarmo COBALT cor/r- POUNDS T CDBALT ACETATE AND/GR COBALT PRGPEONATE Bernard H. Gwynn, Gibsonia, William A. Pardee, Fox

Chapel Borough, and John V. Ward, Oalnnont Borough, P2,, assignors to Gulf Research & Development ompany, Pittsburgh, Pa., a corporation of Delaware Filed Get. 16, 1962, Ser. No. 230,969 3 Claims. (Cl. 26%439) This invention relates to a process for converting cobalt compounds in an aqueous solution to cobalt acetate and/or cobalt propionate.

In the 0x0 process a mixture comprising hydrogen, carbon monoxide and an olefin is reacted at an elevated temperature and an elevated pressure in the presence of a catalytic amount of a cob-alt compound to obtain a mixture predominating in an aldehyde having one more carbon atom than the reactant olefin having dissolved therein the cobalt catalyst. After the unreacted hydrogen and carbon monoxide are removed from the aldehyde product, it is treated to remove therefrom the d ssolved cobalt compound. The aldehyde product remaining 18 then treated at an elevated temperature and pressure with hydrogen in the presence of a hydrogenation catalyst, such as nickel, to convert the aldehyde to the corresponding alcohol.

The soluble cobalt catalyst can be removed from the crude aldehyde product obtained in the first stage of the oxo process by contacting the same with water at an elevated temperature and pressure. A procedure for carrying out the first stage of the oxo process and thereafter removing cobalt catalyst from the crude aldehyde product using water therefor is described in U.S. Patent No. 2,978,513 of Carter et al. dated April 4, 1962. The cobalt compounds in such case which are believed to be present in the crude aldehyde product, in percent by weight based on the total cobalt compounds in the aldehyde product, are as follows: 60 to 80 percent cobalt hydrocarbonyl, HCo(CO) to 30 percent dicobalt octacarbonyl, [Co(CO) one to five percent cobalt formate Co(OOCH)- and one to five percent cobalt dicobalt octacarbonyl, Co[Co(CO) The cobalt compounds, as a result of the water treatment, find themselves almost completely in the water removed from the demetalling zone and therefore a decobalted aldehyde product, useful in itself, or suitable for hydrogenation to the corresponding alcohol product is obtained.

The cobalt compounds in the water issuing from the decobalter are toxic and therefore present a sewage disposal problem. The cobalt compounds could, upon proper treatment, be converted to oil-soluble cobalt compounds suitable for reuse in the first stage of the 0x0 process.

Conversion of these cob-alt compounds to water-soluble cobalt acetate or cobalt propionate would provide a solutin to these problems. Cobalt acetate and cobalt propionate are not toxic and therefore the problem of sewage disposal would be facilitated. Of if desired the aqueous solution containing cobalt acetate or cobalt propionate could be heated, for example, in the presence of 2- ethylhexanoic acid and sodium hydroxide to obtain the cobalt salt thereof which could be recovered and employed in the first, or hydroformy lation stage, of the oxo process.

If an attempt is made to incorporate acetic acid or propionic acid in the water employed in the decobalting operation in order to convert the cobalt compounds in 3,246,024 Patented Apr. -12, 1966 the crude aldehyde product to cobalt acetate or cobalt propionate, we have found that only a small amount of the cobalt compounds will be converted to the desired cobalt salts, irrespective of the amount of acetic acid or propionic acid present. We have also found, however, that if additionally the water containing the small amount of cobalt acetate or cobalt propionate is treated with molecular oxygen in the presence of a selected amount of acetic acid or propionic acid the remaining cobalt compounds will be converted to cobalt acetate or cobalt propionate. An aqueous solution of cobalt acetate or cobalt propionate will be obtained which can then be discarded or further employed as desired.

In order that the process of this invention may be understood more fully reference is made to the accompanying drawing which illustrates a preferred embodiment thereof.

Referring to the drawing a crude aldehyde product such as would be obtained from the low pressure separator in the aforesaid U.S. Patent No. 2,978,513, and containing the cobalt compounds described hereinabove, is led by line 2, provided with orifices 4, into the lower portion of demetalling zone 6. Water is introduced into the upper portion of demetalling zone 6 by line 8. Acetic acid or propionic acid is introduced into water line 8 by line 10. Acetic acid or propionic acid, or combinations thereof, though not preferred, are employed since the cobalt salts thereof are Water soluble. The cobalt salts of the higher organic acids are not water soluble and would result in undesired cobalt deposits in the demetalling zone. The demetalling zone is maintained substantially full of water and the level thereof 12 is held slightly below the top of the demetalling zone. The demetalled hydroformylation reaction product, being lighter than the water, will move upwardly therethrough, float on the surface thereof and be continuously removed from the demetalling zone 6 by line 14. The demetalled aldehyde product can, if desired, be subjected to hydrogenation conditions to convert the aldehyde to the corresponding alcohol. The hot water, on the other hand, will move downwardly through the demetalling zone and be continuously removed therefrom by line 16.

The temperature in demetalling zone 6 must be high enough to permit reaction of the acetic acid or propionic acid with the cobalt compounds, to the extent such reactions can proceed therein, but not so high that thermal decomposition of the cobalt compounds and the formation of cob-alt metal will result. Thus a tem perature of about 225 to about 280 F. can be employed. A pressure of about to about 300 pounds per square inch gauge can be used. The droplets of crude aldehyde product rising in the demetalling zone are maintained within a range of about to about /2 inch in diameter. The contact time of the aldehyde droplets with the aqueous medium is at least about Arminute but preferably about /2 to about five minutes. The amount of fresh water employed can vary over a wide range but must be at least about /2, preferably about one to about three, percent by weight relative to the crude aldehyde product on a flow basis. There is an inventory of Water retained in demetalling zone 6 which is about equal in volume to the hourly hydroformylation reaction product flow volume.

As noted, under the conditions existing in demetalling zone 6 only a small portion of the cobalt compounds in the crude aldehyde product will react with the acetic acid a or the propionic acid to form the corresponding cobalt salts. We believe only the cobalt dicobalt octacarbonyl of the cobalt compounds in the crude aldehyde product reacts with the acetic or propionic acid in the demetalling zone, as shown, for example, in the following equation, to form cobalt acetate or cobalt propionate:

Additionally the dicobalt octacarbonyl in the crude aldehyde product can complex with the water in the demetalling zone and the complex, in the presence of additional water, can form insoluble cobalt hydroxide which can precipitate to form objectionable deposits therein. Acetic or propionic acid will, however, react preferentially under the defined conditions with the water complex and a Water soluble compound will be obtained.

In the subsequent treatment of the water product from demetalling zone 6, which will be described hereinafter, the cobalt hydrocarbonyl will decompose as follows:

The cobalt obtained in Equation 2 will immediately react with oxygen in accordance with the following:

Cobalt oxide obtained in Equation 3 will then react with acetic acid, or propionic acid, as follows, to obtain cobalt acetate:

The net result of the desired reactions in the demetalling zone, Equation 1, and in the oxidation reactor, Equations 2, 3 and 4, to be described, is therefore as follows:

From the above it is apparent that sufficient acetic acid, or propionic acid, must be added to demetalling zone 6 to satisfy Equation 1 and to react with dicobalt octacarbonyl water complex formed therein and thus convert the same to cobalt acetate or cobalt propionate. The remainder of the acetic acid or propionic acid employed in the process is that sufficient to satisfy Equation 4, and this additional acid can of course be added to the oxidation reactor. However, in order to simplify the operation and to assure that more than enough acetic acid or propionic acid will be present in demetalling zone 6 suflicient to satisfy the defined demands therein, we add all of the acetic acid or propionic acid that will be required in the entire process in line 10. The amount of acetic acid or propionic acid which will be added in line 10 therefore, calculated as 100 percent acid, will amount to at least the stoichiometric requirements to form cobalt acetate or cobalt propionate, preferably about one and one-half to about three times the stoichiometric requirements, based on all of the cobalt present in the varied cobalt compounds in the crude aldehyde product introduced into demetalling zone 6.

The water leaving demetalling zone 6 by Way of line 16, carrying the defined cobalt compounds, including cobalt acetate or cobalt propionate and at least sufficient additional acid to satisfy Equation 4, is then passed into the base of oxidation tower 18. A gas containing molecular oxygen, such as air, is also introduced into the base of oxidation tower 18 by line 20. If desired the gas containing molecular oxygen can be dispersed therein in any suitable manner. The amount of oxygen required will be at least that suflicient to satisfy the needs of Equation 3. In general at least about 100 percent excess, preferably about 100 percent to about 500 percent excess, based on the cobalt content of the system is required. The pressure can vary over a wide range, from about 0 to about pounds per square inch gauge, although atmospheric pressure is preferred. The temperature re quired can also vary over a wide range, from about 150 to about 250 F. The amount of time required to effect the desired reaction in oxidation reactor 18 can also vary over a wide range and will be dependent upon What additional results are desired therein. In the event it is desired merely to convert the remainder of the compounds in the water to cobalt acetate or cobalt propionate a reaction time of at least about 10 minutes, but preferably about 30 to about 60 minutes, is sufiicient. If, however, it is desired to concentrate the cobalt acetate or cobalt propionate in the water, as in the preferred embodiment, then additional heat must be supplied to evaporate the amount of water desired in order to coneentrate the cobalt acetate or cobalt propionate solution. In any event it is preferred that a high temperature be employed. The advantage of the operation defined herein resides in the fact that a high temperature, and a long residence time if required, can be employed since the Water containing the cobalt compounds being treated is free of hydrocarbons which might decompose or other wise be adversely affected under such conditions of temperature and time.

In the preferred embodiment wherein the final solution containing the cobalt salts is concentrated, for example at a temperature of about 225 F. and a pressure of about 0 pounds per square inch gauge, water vapor, containing either free acetic acid or propionic acid is removed overhead from oxidation reactor 18 by line 22 and thereafter passed through condenser 24 wherein it is cooled to a temperature of about to about F. The liquid is removed from the system by line 26 and gaseous products by line 28. The water containing cobalt acetate or propionate is removed from oxidation reactor 18 by line 30 and then through a cooler 32 wherein the concentrated solution is cooled from a temperature of about 225 to about 110 F. From cooler 32 the water is passed by line 34 into storage tank 36. The concentrated aqueous solution of cobalt acetate or cobalt propionate is removed from the system by line 38.

The process of this invention can further be illustrated by the following. To water which had been in contact with a crude hydroformylation reaction product and contained cobalt in the form of cobalt hydrocarbonyl there was added acetic acid. Four hundred and three grams per hour of this solution, analyzing one percent by weight of cobalt, 4.8 percent by weight of acetic acid and the remainder water, was passed upwardly through a tower eight feet high and having an internal diameter of one inch. At the same time five cubic feet of air per hour was passed upwardly through the tower. The tower Was maintained at a temperature of 200 F. by external means and at atmospheric pressure. Overhead there was recovered 96.5 grams per hour of an aqueous solution containing 3.6 percent by weight of cobalt in the form of cobalt acetate, 4.3 percent by weight of acetic acid and the remainder water. The remainder of the water not in the latter aqueous solution was driven off overhead as steam. Discrepancies in the material weight balance were due to the difficulty of completely analyzing the cobalt hydrocarbonyl in the charge and to mechanical losses of liquid in the unit. However, all of the cobalt in the treated material was in the form of cobalt acetate.

Obviously many modifications and variations of the invention, as hereinabove set forth can be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. A process for converting an aqueous solution containing cobalt carbonyls to an aqueous solution containing a cobalt salt selected from the group consisting of cobalt acetate and cobalt propionate which comprises subjecting said aqueous solution to oxidation with molecular oxygen sole in the presence of an organic acid selected from the group consisting of acetic acid and propionic acid.

References Cited by the Examiner UNITED STATES PATENTS Spence 260-604 Mertzweiller et a1. 260604 Mertzweiller 260439 Rehn et a1. 260604 TOBIAS E. LEVOW, Primary Examiner, 

1. A PROCESS FOR CONVERTING AN AQUEOUS SOLUTION CONTAINING COBALT CARBONYLS TO AN AQUEOUS SOLUTION CONTAINING A COBALT SALT SELECTED FROM THE GROUP CONSISTING OF COBALT ACETATE AND COBALT PROPIONATE WHICH COMPRISES SUBJECTING SAID AQUEOUS SOLUTION TO OXIDATION WITH MOLECULAR OXYGEN SOLE IN THE PRESENCE OF AN ORGANIC ACID SELECTED FROM THE GROUP CONSISTING OF ACETIC ACID AND PROPIONIC ACID. 